1. Field of the Invention
The present invention relates to a light-transmitting module, in which includes an electronic device for driving the light-emitting device within the package.
2. Related Prior Art
In an optical transmitting module with a compact size, a CAN type package is widely used. The CAN type package contains a light-emitting device and a light-receiving device therein. The light-emitting device is electrically connected to a lead accompanied with the CAN type package, and is driven by a driver circuit provided outside thereof. The light-receiving device, which monitors light emitted from the light-emitting device, is also connected to another lead.
In such configuration that the driver circuit is provided outside of the module, the driving signal transmitted from the driver circuit to the module is deformed due to the impedance mismatching. That is, any transmission line intrinsically has transmission impedance, and when the transmission impedance does not match with an input impedance of the module, the signal transmitted in the transmission line may be deformed by a reflection at the input of the module, thereby degrading an optical output of the light-emitting device.
Moreover, when the driving signal is over giga-hertz (GHz), the light-emitting device, such as a semiconductor laser diode, must be supplied 50 mA or more as an AC current for modulating the laser diode. Such large current may cause an electro-magnetically-induced noise.
If a transistor for driving the light-emitting device is installed within the same package, in which the light-emitting device is enclosed, the transistor and the light-emitting device can be positioned immediately close to each other, which reduces the impedance mismatching effect. However, it is hard to install the transistor within the small sized package the conventional transmitting module generally uses.
Therefore, one object of the present invention is to provide an optical transmitting module in which an electronic active device for driving a light-emitting device is integrally enclosed within a same package with that the light-emitting device is installed.